1. Field of the Invention
The present invention relates to an aerodynamic garment, such as a suit, for improved athletic performance and method of manufacture. More particularly, the present invention relates to a garment formed from textiles that are optimized to specific speed ranges and the speed of a particular body area as well as the frontal areas of the body segments so as to minimize air resistance and pressure drag.
2. Background of the Invention
In high-speed individual sports, such as speed skating, skiing, bicycling and running, air resistance or drag is major force acting against the athlete and the wind resistance significantly retards the speed of the athlete.
In sprint and middle distance running, systematic attempts to reduce aerodynamic drag have been sporadic. Most efforts have focused on running technique. Apparel-related methods of reducing drag center on altering the shape an athlete presents to the drag-producing air stream.
The energy required to overcome drag at sprint (10 m/s) and middle distance (6 m/s) speeds has been estimated to range between 13.6%, and 3% respectively, of the total energy expenditure in running. The energy expenditure to overcome drag for bicycle racing is an even greater percentage of the total energy expenditure for speeds in excess of 20 miles/hour.
The drag force on an athlete is the same as that on any other speeding object such as a bullet or an airplane, and is given by:
Fd=0.5pApCdV2xe2x80x83xe2x80x83(Equation 1)
where Fd is the drag force (measured in Newtons); p is the air density (kg/m3); Ap is the projected or frontal area of the athlete normal to the wind (m2); Cd is a non-dimensional drag coefficient determined by the geometric orientation and shape of the body, and V is the body velocity in still air (m/s). Drag force has pressure and frictional components. Friction drag is due to surface imperfections while pressure drag results from pressure differences between the wind facing and trailing surfaces of a body.
Air pressure is reduced in trailing regions wherever the airflow separates from the surface and leaves a low-pressure cavity. Such pressure differences, acting perpendicularly to the surface, cause large retarding forces. The drag force as exemplified in Equation 1 shows that drag increases proportional to the square of velocity. Power is proportional to the product of the drag force and velocity, so that the power required to overcome retarding forces and drive an athlete through the air increases as the cube of velocity. Consequently, doubling the forward velocity of an athlete requires an eight-fold increase in energy expenditure to overcome drag.
As is evident from Equation 1, a reduction in air density, projected area or drag coefficient will decrease drag and allow maintenance of a higher forward velocity without additional energy expenditure. The effect of reduced drag is most apparent in races conducted at a high altitude, such as at Mexico City, where air density is decreased approximately 23% from sea level.
Other than by drafting or racing at high altitude, a reduction in drag force will only be achieved by presenting a more streamlined shape to the wind (reduce the value of Ap). Good examples of techniques to reduce Ap are the crouched postures of downhill skiers, cyclists and speed skaters. The adoption of a full crouch position, compared with an upright position, has been estimated to provide a time saving of nearly three minutes in a 40 km cycling time trial at a velocity of 13.4 m/s.
Loose or baggy clothing can increase the drag area and aerodynamic drag on a runner, cyclist or Nordic skier by up to 41%. A skintight suit that covers body hair and eliminates the protrusions, flaps and edges of traditional loose apparel will reduce the Ap of an athlete. To be effective, the suit must fit the body tightly, particularly in the position of movement. By presenting only smooth, unwrinkled fabric to the wind facing portions of the body the so-called xe2x80x9cwet edgesxe2x80x9d of airflow, aerodynamic drag can be further minimized.
In many athletic events, the difference between winning and losing can come down to a fraction of a second. An athlete using apparel that can reduce aerodynamic drag can potentially bridge the gap between winning and losing. An improved body suit for an athlete that reduces aerodynamic drag was thus needed.
These obstacles are addressed by the present invention, which is directed to an aerodynamic suit for improved athletic performance, and a method of manufacturing the suit.
Each body segment is assigned a Reynolds number based upon the velocity and size of the body segment. Each body segment has an appropriate textile assigned to it. The texture of the textile is appropriate to the Reynolds number. As a result, each body segment should go through transition simultaneously during the athletic event to minimize drag flow.
The limbs of the suit may be cut so that the seams between the limbs and the rest of the suit are at angles parallel to the direction of movement when at estimated maximum velocity to thereby reduce creases and aerodynamic drag resulting therefrom.
From the foregoing, it is an object of the present invention to provide an athletic suit having body segment Reynolds numbers matched with fabric to reduce the body segment drag coefficient in the range of Reynolds numbers experienced by the body segment during the intended athletic activity.
Another object of the present invention is to provide a method of manufacturing an athletic suit having body segment Reynolds numbers matched with fabric to reduce the segment drag coefficient in the range of Reynolds numbers experienced by the body segment during the intended athletic activity.
Yet another object of the present invention is to provide an athletic suit in which the athlete will experience an early transition of laminar to turbulent airflow during the intended athletic activity.
Still another object of the present invention is to provide an athletic garment made from at least two different fabrics that cover different body segments of the athlete. The fabrics are selected based upon the ranges of speeds of the body segments during an athletic event to minimize coefficients of drag experienced by each of the body segments during said athletic event.